Question

An 80 kilogram person leaps 17 centimeters and a 90 kilogram person leaps 14 centimeters. Which person has the greater potential energy at the top of their jump? How do you determine this?

Answer 1

What you need to do first is carefully look at what you are being asked. The key component here is "Which person has the greater potential energy at the top of their jump?" and the operative word is "top".
So, what you really have is an 80kg weight dropping 17cm and a 90kg weight dropping 14cm.
You know that PE=mgh, with m=mass, g=gravity, h=height, so your PE for each person should look something like this:
\[PE _{1} = 89kg * 9.8m/s * .17m\]
\[PE _{2} = 90kg * 9.8m/s * .14m\]
Giving you \[PE _{1}=148.274J\] and \[PE _{2}=123.48J\]
Assuming you are ignoring air friction.

Answer 2

Thanks. I'm a little confused as to why you used 89 instead of 80 though. Can you please explain?

Answer 3

A typo.